Package Wrapping Machine with Detection of Lip Features of Trayed Products to be Wrapped

ABSTRACT

A package wrapping machine includes a wrapping station where film is to be manipulated during a packaging operation. A support is provided for holding rolled film, the support located to permit film to be drawn into the wrapping station. A sensor arrangement detects package size data that is used to set one or more wrap parameters.

TECHNICAL FIELD

This application relates generally to packaging machines for placingfilm around products and more particularly to a packaging machine thatdetects and takes into account tray lip height and/or trayed itemleading edge to tray bottom wall leading edge distance before wrapping.

BACKGROUND

Packaging machines are frequently used to automatically wrap film aboutproduct, such as trayed food items. The packaging machines often includea film gripper that grips and pulls the film from a roll of film, sideclamps that grip the film and folders that fold the film underneath theproduct. Various control systems and sensors may be employed, forexample, to control operation of the gripper and to sense productlocation.

In circumstances where food product such as meat is being wrapped,various types of trays can be used to hold the meat. Trays havingsimilar projected footprints when viewed from the top can have differentactual footprints due to differing tray depths. Moreover, it is possiblethat in some cases the food product may accidentally hang over the sideof the tray. Obtaining a high quality wrap for each product isimportant, and can be affected by variances between products such as lipheight and trayed item leading edge to tray bottom wall leading edgedistance before wrapping.

SUMMARY

In one aspect, a package wrapping machine includes an infeed station atwhich trayed items to be wrapped are placed. A conveying system movestrayed items into the machine and to a wrapping station where film ismanipulated to wrap the trayed items. A sensor arrangement detectstrayed items moved by the conveying system. A controller is associatedwith the sensor arrangement and operates to identify tray lip height fortrayed items based upon outputs from the sensor arrangement. Thecontroller setting one or more wrap parameters based upon identifiedtray lip height.

In another aspect, a package wrapping machine includes an infeed stationat which trayed items to be wrapped are placed. A conveying system movestrayed items into the machine and to a wrapping station where film ismanipulated to wrap the trayed items. A sensor arrangement detectstrayed items moved by the conveying system. A controller is associatedwith the sensor arrangement and operates to identify a distance betweena trayed item leading edge and a trayed item bottom leading edge basedupon outputs from the sensor arrangement. The controller sets one ormore wrap parameters based upon the identified distance.

In a further aspect, a package wrapping machine includes an infeedstation at which trayed items to be wrapped are placed and a conveyingsystem for moving trayed items into the machine and to a wrappingstation where film is manipulated to wrap trayed items. A sensorarrangement is provided for detecting trayed items moved by theconveying system. A controller is associated with the sensor arrangementand operable to identify at least one of a trayed item volume or atrayed item center of gravity location based upon outputs from thesensor arrangement. The controller setting one or more wrap parametersbased upon the identified trayed item volume or trayed item center ofgravity location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, perspective view of an embodiment of a packagewrapping machine;

FIG. 2 is a schematic front elevation of a trayed item moving through apackage size and position sensor arrangement of the machine of claim 1;

FIG. 3 is a schematic side elevation of FIG. 2;

FIG. 4 is a schematic front elevation detailing light sensor anddetector cooperation; and

FIG. 5 is a top schematic view of a trayed item moving upward throughfilm with underfolders moved into position to frame the trayed item.

DETAILED DESCRIPTION

Referring to FIG. 1, a package wrapping machine 10 includes an in-feedportion 12 at which a product such as a trayed food item can beintroduced to the machine 10, a wrap station 16 at which the product canbe wrapped, e.g., by a wrap film such as a food contact grade film, andan out-feed portion 18 at which the wrapped product can be accessed toremove the product from the machine 10. The wrap station 16 includes anadjacent support for holding rolled film 14 and mechanisms (e.g., filmgrippers and underfold plates) for manipulating the film during apackaging operation. The support is located to permit film to be drawnoff the roll 14 and into the wrapping station and a film grip assembly(not shown) is used for gripping at least one edge of film during atleast part of a packaging operation.

More specifically, and as described in U.S. Pat. No. 6,851,250, theentirety of which is hereby incorporated by reference, a package is fedinto the machine at an infeed station 12 and is moved rearward by aconveying system 20 to an elevator. The infeed station may include aweighing mechanism and the conveying system may be adjustable to centerthe package on the elevator as described in U.S. Pat. No. 6,851,250.

A raised position of the elevator at least partially defines the wrapstation 16. Before or when the package reaches the wrap station, a filmgripper and side-clamps cooperate to draw an appropriate amount of filmfrom a source roll out over the wrap station and to stretch the film ina desired manner. The amount of drawn film is determined by packagesize. The elevator 22 then moves the package up through a plane of thestretched film and the film is wrapped around the package by front, rearand side folding members. The wrapped package is moved onto a heatsealing conveyor 24 that receives and seals the wrapped film at thebottom of the package. Other wrapping machine variations havingdifferent wrapping station configurations could also be utilized.

Referring now to FIGS. 2 and 3, an exemplary package size and positionsensor arrangement 30 located along the infeed conveying system isshown, where direction of travel of the trayed item 32 is into the page.The arrangement 30 may be positioned proximate to that portion 26(FIG. 1) of the machine housing into which items are conveyed. The sizeand position sensor arrangement of FIG. 2 includes a light source 34mounted below the conveyor 36 (shown as a series of spaced apart, narrowconveyor belts that permit light to flow upward through the conveyor.The light source may be, for example, an elongated light bulb that hasbeen coated such that light 38 from the bulb escapes only upward andtoward a pair of spaced apart cameras 40. The cameras 40 may, by way ofexample, be line scan cameras that are arranged with overlapping fieldsof vision. The cameras and light source create a light plane throughwhich the trayed item 32 passes when moving toward the elevator. Eachline scan camera may output pixel scan data identifying which pixels ofeach camera are blocked by the trayed item 32 from receiving light fromthe source 34. By adding the number of OFF pixels from each camera awidth of the trayed item can be determined, with each OFF pixelcorresponding to a corresponding width measurement. The OFF pixel countcan be adjusted by any known overlap between the line scan cameras. Therelative number of OFF pixels as between the two line scan cameras 64also indicates the lateral position of the trayed item on the conveyor.

The belts of the conveyor 36 will block some pixels to the sides of thetrayed item 32. However, because the belts are made much more narrowthan any package to be wrapped, a small, defined number of blockedpixels in sequence can be interpreted as a conveyor belt anddisregarded.

It is recognized that the height of the trayed item, combined with theangle of the tray wall 50 below the tray lip 52, could impact the widthmeasurement. Accordingly, the size and position sensor arrangement alsoincludes a series of side located IR emitters 54 and corresponding sidelocated IR detectors 56. While five emitters and corresponding detectorsare shown, the number could vary as desired for any application. Forexample, the number and vertical proximity of the emitter and detectorpairs could be increased to provide better detection of tray profile,which will be described below. The emitters and detectors set up aheight detection plane. As shown in FIG. 3, where movement of the trayeditem is right to left, in one example the height detection plane 62 issubstantially vertical and the width detection plane 64 is angled,crossing the height detection plane 62. The trayed item may typically bemoved by a pusher paddle 66 associated with the conveyor. The front lipof a trayed item will typically cross, and be detected by, the sensorsof the height detection plane, enabling the length (i.e, dimension d1 inthe direction of right to left travel in FIG. 3) of the trayed item 32to be determined because the position of the paddle 66 is known. In acase where a tray lip is at a height such that it is pushed by thepaddle 66, the length dimension is simply the distance of the paddlefrom the height detection plane 62 at the time the lip of the trayeditem is detected in the plane 62. Where the tray lip is at a heightabove the height of the paddle 66, then the actual length of the trayeditem (i.e. from lip edge to lip edge) will be slightly greater than thedistance of the paddle 66 from the plane 62. The sensor arrangement mayaccount for this difference by using the detection plane to determine aprofile of the tray.

Referring to FIG. 4, where travel direction of the trayed item 32 isagain into the page, each light emitter 54 outputs a field of light thattends to impinge upon the light sensor 56 directly across from it, aswell as the light sensors immediately above and below such light sensor.Thus, entry of the tray lip 52 into the height detection plane 62 (FIG.3) will block some light to at least some of the light sensors 56,enabling detection of the presence of the lip in the plane. Continuedmonitoring of changes in light detected by the light sensors 56 as thetray wall 60 enters the plane enables detection of the angle of the traywall 60, the horizontal extension of the lip 52 from the tray wall 60and the height of the lip 52. By determining these dimensions, asuitable tray length dimension adjustment can be made for those trayeditems in which the paddle 66 (FIG. 4) contacts the tray wall 60 ratherthan the tray lip 52. With respect to lip height, detection of entry ofthe upper end of tray wall 60 (FIG. 3) into the height detection plane62 is used to identify the lower edge of the lip. In this manner, properlip height detection is not adversely impacted by food product“overhang” that occurs when food product is resting atop the lip. Suchoverhanging food product may or may not extend beyond the perimeter ofthe tray defined by the edge of lip. In such overhang cases, the heightof the food product resting on the lip could inadvertently be identifiedas the lip height. By identifying the lower edge of the lip and usingthat identification as the indication of lip height, h1, the effect ofany food product overhang is avoided. The determined height, h1, can beused to make appropriate adjustments to the width measurement by thecameras 40.

It is also desirable to identify the distance, d2, between the edge ofthe tray lip and the edge of the tray bottom. This distance can bedetermined by the difference between the position of the paddle 66 whenthe height detection plane 62 is first broken by the tray and theposition of the paddle when the lowest light detector 56 no longerreceives light (e.g., because the lower end of the tray wall has brokenthe height detection plane). Some minor compensation can be made to thisdetermined difference based upon the height of the lowest detector 56and the angle of the tray wall 60. In cases where product overhangactually extends beyond the leading edge of the tray lip 52, thedetermined distance d2 will take into account such overhang.

The package dimension and position determinations discussed above can beused to control various wrap parameters of the machine. A wrappingmachine may include a controller that uses the determinations to specifya WrapBox for a given trayed item, where the WrapBox may identify aspecific tray size. Trays of the same family have the same width andlength dimensions, but have different tray heights. Thus, the lip heightdetermination, h1, can be used to assure that the proper tray size isselected. This result can be achieved by using the tray length and widthdeterminations to identify the correct tray family, and then comparingthe lip height to certain lip height windows associated with the traysizes making up that tray family. By selecting the proper tray size,other wrapping parameters can be modified to achieve a better wrap forthat tray size. For example, wrap parameters such as prepositioning ofthe film underfolders (see side underfolders 70 and 72, rear underfolder74 and front underfolder 76 in FIG. 5) as the trayed item is movedupward through the plane of wrap film 78 that has been pulled from thefilm roll 80, and subsequent repositioning of the underfolders forbeginning the wrap can be modified to achieve better wrap quality.

In one implementation, the front underfolder 76 is premoved with a gapdistance between its edge and the edge of the tray coming up to movethrough the film. When the package hits peak height, the frontunderfolder 76 will move towards the package and close the gap to keepthe package secure while the wrap process occurs. Large lip trays willhave gap around the tray just like any other, but when a large lip trayreaches peak, the front underfolder closes in to the edge of the trayplus a distance proportionate to the lip height, removing the gap andslightly undercutting the edge of the tray. Small lip trays, will closethe gap and attempt to justify the edge of the tray lip with the edge ofthe front folder.

The determined distance, d2, is also useful in setting wrap parameters.For example, the premove of the rear underfolder 74 will maintain thegap between the underfolder and the package edge as the edge passesupward reaches peak height. The distance d2 is used to control filmtension when the rear underfolder 74 is ready to complete the underfold.Specifically, distance d2 is used to move the rear underfolder 74slightly under the base of the tray to tuck the film under the tray andtack the film to the rear edge of the tray bottom. The film cuttingknife 82 will fire and the rear underfolder 74 will complete itsunderfold process. Without the distance d2, any attempt to close the gapand tuck the film prior to a knife cut and full underfold could resultin inconsistent tensions of film ranging from opens to tensions so highthat the rear cannot scoop under the tray at all, potentially resultingan a crush. By identifying distance d2, the film can be tucked under tothe same distance under the base of each tray.

Other wrap parameters such as film stretch %, position on elevator, sideclamp open timing, knife fire timing, overall wrap speed, dischargespeed, and side underfolder adjustments could also be set in accordancewith measurements made by the package size and position sensorarrangement.

It is to be clearly understood that the above description is intended byway of illustration and example only and is not intended to be taken byway of limitation, and that changes and modifications are possible. Forexample, the sensor system described above can be used to determine orapproximate the volume of the tray/product combination (e.g., byconsidering product width as determined by detection plane 64 incombination with the overall height profile as determined as the trayedproduct passes through detection plane 62) and allow the wrapper to makewrapping decisions (e.g., set wrap parameters) based upon such volume.Further, the sensor system can determine or approximate the location ofthe center of gravity (assuming all of the product is of equal weight)of the tray/product combination (e.g., by considering the overall heightprofile as determined as the trayed product passes through detectionplane 62) and allow the wrapper to make wrapping decisions (e.g., setwrap parameters) based upon such center of gravity location. Otherembodiments are contemplated and modifications and changes could be madewithout departing from the scope of this application.

1. A package wrapping machine for handling trayed items, each trayeditem including product within a tray that has a tray lip, the machinecomprising: an infeed station at which trayed items to be wrapped areplaced; a conveying system for moving trayed items into the machine andto a wrapping station where film is manipulated to wrap trayed items; asensor arrangement for detecting trayed items moved by the conveyingsystem; a controller associated with the sensor arrangement and operableto identify tray lip height for trayed items based upon outputs from thesensor arrangement, the controller setting one or more wrap parametersbased upon identified tray lip height.
 2. The package wrapping machineof claim 1 wherein the sensor arrangement includes sensors defining asubstantially vertical detection plane and sensors defining an angleddetection plane.
 3. The package wrapping machine of claim 2 wherein theangled detection plane crosses the vertical detection plane.
 4. Thepackage wrapping machine of claim 2 wherein the substantially verticaldetection plane is defined by multiple light emitters spaced apartvertically and located to one lateral side of the conveying system andmultiple light sensors spaced apart vertically and located to anopposite lateral side of the conveying system, and the angled detectionplane is defined by a light source located below the conveying systemand at least two cameras located above the conveying system.
 5. Thepackage wrapping machine of claim 1 wherein identified lip height isused by the controller to identify a specific tray size.
 6. The packagewrapping machine of claim 1 wherein the position of at least one filmunderfolder of the wrap station is controlled based at least in partupon the identified lip height.
 7. The package wrapping machine of claim1 wherein trays carrying trayed items include a tray lip, an angled traywall and a tray bottom, lip height is identified at least in part bydetecting the angled tray wall.
 8. The package wrapping machine of claim7 wherein the tray wall is detected by sensors defining a substantiallyvertical detection plane.
 9. The package wrapping machine of claim 1wherein the controller is further operable to identify a distancebetween a trayed item leading edge and a tray bottom wall leading edgebased upon outputs from the sensor arrangement, the controller settingone or more wrap parameters based upon the identified distance
 10. Apackage wrapping machine comprising: an infeed station at which trayeditems to be wrapped are placed; a conveying system for moving trayeditems into the machine and to a wrapping station where film ismanipulated to wrap trayed items; a sensor arrangement for detectingtrayed items moved by the conveying system; a controller associated withthe sensor arrangement and operable to identify a distance between atrayed item leading edge and a tray bottom wall leading edge based uponoutputs from the sensor arrangement, the controller setting one or morewrap parameters based upon the identified distance.
 11. The packagewrapping machine of claim 10 wherein the sensor arrangement includessensors defining a substantially vertical detection plane and sensorsdefining an angled detection plane.
 12. The package wrapping machine ofclaim 11 wherein the angled detection plane crosses the verticaldetection plane.
 13. The package wrapping machine of claim 11 whereinthe substantially vertical detection plane is defined by multiple lightemitters spaced apart vertically and located to one lateral side of theconveying system and multiple light sensors spaced apart vertically andlocated to an opposite lateral side of the conveying system, and theangled detection plane is defined by a light source located below theconveying system and at least two cameras located above the conveyingsystem.
 14. The package wrapping machine of claim 10 wherein theposition of at least one film underfolder of the wrap station iscontrolled based at least in part upon the identified distance.
 15. Thepackage wrapping machine of claim 10 wherein trays carrying trayed itemsinclude a tray lip, an angled tray wall and a tray bottom wall, thedistance is identified at least in part by detecting the angled traywall.
 16. The package wrapping machine of claim 15 wherein the sensorarrangement includes vertically spaced apart sensors defining asubstantially vertical detection plane, the distance is identified basedupon a trayed item first breaking the substantially vertical detectionplane and the angled wall of the trayed item obstructing a lowest one ofthe vertically spaced apart sensors.
 17. The package wrapping machine ofclaim 10 wherein the trayed item leading edge is defined by either (i)the leading edge of the tray lip or (ii) product overhanging beyond theleading edge of the tray lip.
 18. A package wrapping machine comprising:an infeed station at which trayed items to be wrapped are placed; aconveying system for moving trayed items into the machine and to awrapping station where film is manipulated to wrap trayed items; asensor arrangement for detecting trayed items moved by the conveyingsystem; a controller associated with the sensor arrangement and operableto identify at least one of a trayed item volume or a trayed item centerof gravity location based upon outputs from the sensor arrangement, thecontroller setting one or more wrap parameters based upon the identifiedtrayed item volume or trayed item center of gravity location.